Devices having a variable colour output are known in the art. US2007273265 for instance discloses a light emitting device with variable output colour. More specifically, this document describes a colour conversion cell which can be positioned in front of a light source in order to generate other colours or colour temperatures. Typically the light source is a light emitting diode (LED) which is power efficient but emits in a narrow and fixed spectra. The new colours are generated by photoluminescence in fluorescent dyes contained in the cell. The colour converting of the cell is electrically controllable, preferably by controlling the orientation, density or distribution of the fluorescent dyes, or by controlling a path length of the light in the cell.
Further, WO2007069142 describes a light-emitting device for emitting light having a desired colour point, comprising at least one solid-state light source, at least one light-converting element, a light guiding arrangement and a switch control unit, wherein the solid-state light source is provided for emitting primary radiation, the light guiding arrangement arranged between the solid-state light source and the light-converting element has at least one electro-optical switch for controllably splitting the primary radiation into a first portion and a second portion, the switch control unit is provided for controlling the electro-optical switch or switches for variably adjusting the ratio between the first and the second portion of the primary radiation, and the light-converting element is provided for the partial or complete absorption of at least a first portion of the primary radiation and for the re-emission of secondary radiation.